The present invention relates to a solid-state image pick-up device and, more particularly, to such a device using CCDs (Charge Coupled Devices).
In a conventional CCD image pick-up device of, for example, the interline transfer type, photosensitive pixels or picture element signals are arranged as shown in FIGS. 1A to 1C. In FIGS. 1A to 1C, vertical and horizontal CCD registers for transferring and reading out the pixels are omitted.
FIG. 1A shows a CCD image pick-up device in which pixels are arranged in a typical matrix form. In order to read out the signal charge with this area sensor using the interlace method, for example, the readout operation of signals from pixels A belonging to the field A and the readout operation of signals from pixels B belonging to the field B are alternately repeated.
FIG. 2 shows a schematic plan view of a conventional CCD image pick-up device having a pixel arrangement as shown in FIG. 1A. In this area sensor, pixels P are arranged in a matrix form on a semiconductor substrate of one conductivity type. A vertical CCD register R is arranged linearly for each vertical pixel column. The vertical CCD registers R of 2-phase drive type are shown in the figure. Transfer electrodes .phi..sub.1 and .phi..sub.2 of the respective phases comprise transfer portions .phi..sub.1.sup.T and .phi..sub.2.sup.T and storing portions .phi..sub.1.sup.S and .phi..sub.2.sup.S, respectively, as shown in FIG. 3.
In the pixel arrangement shown in FIG. 1A, the vertical pixel pitch P.sub.V1 is substantially determined by the vertical dimension of the pixels. Therefore, pixels may be packed at high density in the vertical direction. However, since the horizontal pixel pitch P.sub.H1 is determined by the combination of the horizontal dimension of the pixels and the width of the vertical CCD register, the pixels cannot be densely packed in the horizontal direction. Even with the most advanced micronization technique presently available, only about 400 pixels may be arranged horizontally in an area sensor used for a camera with a 2/3 inch optical system.
FIG. 1B shows the pixel arrangement disclosed in U.S. Pat. No. 4,336,556. When two vertically adjacent pixels A and B are paired, the respective pairs are arranged in a checkered pattern. Furthermore, vertical CCD registers (not shown) are formed in zigzag forms to extend between respective pairs of pixels. Note that the pixels A belong to field A while the pixels B belong to field B. Given a horizontal scanning line n, the intervals between the horizontally adjacent pixels are large. For this reason, the pixel signals corresponding to the immediately preceding scanning line (n-1) in the same field are delayed for one horizontal period (1H period) so as to compensate for the intervals between the horizontally adjacent pixels of the horizontal scanning line n. Degradation in horizontal resolution is thus prevented. The horizontal pixel pitch P.sub.H2 in the pixel arrangement shown in FIG. 1B is smaller than the horizontal pixel pitch P.sub.H1 in the pixel arrangement shown in FIG. 1A. This is because the horizontal pixel pitch is determined by a horizontal pitch between a predetermined pixel on a given scanning line and the corresponding pixel on the next scanning line. On the other hand, the vertical pixel pitch P.sub.V2 in the pixel arrangement shown in FIG. 1B is the same as the vertical pixel pitch P.sub.V1 in the pixel arrangement shown in FIG. 1A. However, since one scanning line is synthesized by the two adjacent horizontal scanning lines, the vertical resolution of the area sensor having the pixel arrangement shown in FIG. 1B is significantly lower than that of the area sensor having the pixel arrangement shown in FIG. 1A.
FIG. 1C shows another pixel arrangement disclosed in U.S. Pat. No. 4,336,556 also by the present applicant. Referring to FIG. 1C, the pixels A and B are arranged in a checkered pattern. Furthermore, vertical CCD registers (not shown) are also formed in a zigzag pattern so as to extend between each pair of adjacent pixels. Note also that the pixels A belong to field A and the pixels B belong to field B. Since the signals are read out from the zigzag pixel row by horizontal scanning, the horizontal scanning line also becomes zigzag in form. Therefore, the horizontal pixel pitch P.sub.H3 in FIG. 1C is the same as the horizontal pixel pitch P.sub.H2 in FIG. 1B and is smaller than the horizontal pixel pitch P.sub.H1 in FIG. 1A. The vertical resolution of the area sensor shown in FIG. 1C is better than that of the area sensor shown in FIG. 1B. However, the vertical pixel pitch P.sub.V3 in FIG. 1C is determined by the vertical dimension of the pixels and the vertical dimension of a transfer electrode (not shown) of the vertical CCD register. Thus, the vertical pixel pitch P.sub.V3 is larger than the vertical pixel pitch P.sub.V1 shown in FIG. 1A. In other words, the vertical resolution of the area sensor shown in FIG. 1C is lower than that of the area sensor shown in FIG. 1A.